Elucidation of the replicative pathway of measles virus by means of genetic analysis coupled with characterization of the products of incomplete replication of ts strains. Characterization of disease and immunity patterns following administration of live measles vaccines in populations that are free from exposure to other sources of measles virus. BIBLIOGRAPHIC REFERENCES: Characterization of Temperature-Sensitive Mutants of Measles Virus: Temperature-Shift Experiment, Y. Yamazi, F.L. Black, H. Honda, Y. Todome, M. Suganuma, E. Watari, H. Iwaguchi and M. Nagashima, Japanese Journal of Medical Science and Biology 28:223-229, 1975. Recombination in Measles Virus, L. Kumari and F.L. Black, Abstract sent to American Society for Microbiology 1976.